The invention pertains to a method for producing an optical fiber spool with a self-supporting coil of an optical fiber according to the preamble of Claim 1, as well as to an optical fiber spool with a self-supporting coil of an optical fiber according to the preamble of Claim 10.
WO2009/036897 A1 discloses a self-supporting optical fiber spool and a method for its production, wherein the optical fiber spool consists of a coil with layered windings of an optical fiber that can be unwound from the interior of the coil. The optical fiber serves for transmitting information between a submarine and a vehicle launched by the submarine such as, e.g., a homing torpedo. In order to provide the optical fiber spool with sufficient stability for maintaining its shape in a self-supporting fashion, the coil of the optical fiber spool is wound up in the form of a cross-winding, wherein the windings of a layer of the optical fiber and the windings of adjacent layers of the optical fiber are fixed on one another by means of an adhesive or adherent binder.
Furthermore, DE 35 20 195 A1 discloses a packaging of cross wrapped layers of a fiber optic. The turns of the fiber optic are connected with each other with an adhesive at least partially. The turns can be displaced by applying a drag force to the fiber optic. Moreover, D1 discloses a method for producing the packaging. In the production an adhesive is applied prior to the winding process of the packaging.
DE 40 17 337 A1 discloses a self-supporting fiber optic coil. Prior to the winding process of the coil, a thermoplastic adhesive is applied to allow the self-supporting of the coil. The particularity of the thermoplastic adhesive is that it is porous and brittle, resulting in a high unwinding speed of the fiber optic cable because of the easy fracturing of the bonded layers.
DE 38 42 036 A1 discloses an optical fiber coil which is self-supporting and in cross winding. Furthermore, the fiber optic is surrounded by a jacket that enables the self-supporting of the coil without an adhesive. Therefore, the jacket is formed by a soft plastic material forming a widened, flattened cross-sectional contour at cross-over points. Furthermore, it is shown to surround the optical fiber with a more rigged plastic with a gel-like intermediate layer between the jacket and the fiber optic. Also, it is disclosed that the jacket has a coefficient of friction, which lies above a value of 0.3. This coefficient of friction results in a self-supporting without adhesive coating.
U.S. Pat. No. 5,179,613 A discloses a method for producing a coil of a fiber optic. In the production the fiber optic is made adherent before winding the coil. For this purpose, it is disclosed that an adhesive is dried after it is applied onto the optical fiber. Before winding, the adhesive is “activated”, in example by heating with a flame.
GB 1 305 690 A shows a self-supporting coil of an insulated electrical conductor whose turns are bounded together to achieve the self-supporting. Furthermore, it is disclosed that the insulation comprises cavities or tranches along its longitudinal axis. Along these cavities or tranches, an adhesive can be moved in the spaces between the turns of the winding. As a bounding agent, a water-based emulsion is disclosed.
In order to transmit information between a submarine or launching platform and a vehicle launched by the submarine or launching platform such as, e.g., a torpedo or an underwater vehicle, the optical fiber is stored in the form of an optical fiber spool in the vehicle, as well as in a so-called cassette that remains on the submarine or on the launching platform. After the vehicle has been launched by the submarine or the launching platform, information is already transmitted through the optical fiber while the optical fiber spool is unwound from the inside toward the outside. The optical fiber spool is wound up in the form of a cross-winding in order to ensure the simple and reliable unwinding thereof. Due to the high unwinding speeds of the optical fiber spool, the simple and reliable unwinding thereof is absolutely imperative for preventing the optical fiber spool from tearing while it is unwound. During the manufacture of the optical fiber spool, the optical fiber spool is wound onto a winding mandrel that needs to be removed after the wind-up process in order to make it possible to unwind the optical fiber spool from the inside toward the outside. The optical fiber spool needs to maintain its shape in a self-supporting fashion after the winding mandrel has been removed.
In the prior art, a gel-like filler or saturant is applied on the optical fiber or individual windings of the optical fiber spool during the wind-up thereof, wherein the filler or saturant is heated referred to the room temperature and solidifies when it cools. It is furthermore known to immerse the optical fiber spool in a dipping bath together with the winding mandrel remaining therein, wherein this dipping bath also consists of a filler or saturant that is heated referred to the room temperature and therefore liquefied. In both instances, cooling of the optical fiber spool results in the filler or saturant being transformed into a gel-like state such that the individual windings or layers of the optical fiber spool adhere to one another and the optical fiber spool therefore maintains its shape in a self-supporting fashion.
In this case, one encounters the problem that the filler or saturant may disperse during the cooling process such that a higher or lower bonding strength or adhesive strength than that required for a reliable unwinding process is produced between the individual layers or individual windings of the optical fiber. If the adhesive force is excessively high, individual layers or individual windings of the optical fiber adhere to one another so solidly that a winding being unwound at a certain time during the high-speed unwinding of the optical fiber already tears along one or more windings from a layer of the optical fiber that should not be unwound until a later time.
Windings that are torn along in this fashion may cause the optical fiber to become knotted and/or sharply bend such that the optical fiber gets stuck, e.g., in the cassette in the submarine or launching platform and is subjected to such a tension that the optical fiber tears as the distance between the submarine or launching platform and the vehicle launched by the submarine or launching platform, e.g., a torpedo or underwater vehicle, increases.
The invention therefore is based on the objective of disclosing a method for manufacturing an optical fiber spool, as well as an optical fiber spool, in which another winding that adheres to the winding currently being unwound with an excessively high adhesive strength is prevented from being torn along.